arm: imx8m: add support for Advantech RSB-3720

Add initial support for Advantech RSB-3720 board.
The initial support includes:
 - MMC
 - eMMC
 - I2C
 - FEC
 - Serial console

Signed-off-by: Darren Huang <darren.huang@advantech.com.tw>
Signed-off-by: Kevin12.Chen <Kevin12.Chen@advantech.com.tw>
Signed-off-by: Phill.Liu <Phill.Liu@advantech.com.tw>
Signed-off-by: Tim Liang <tim.liang@advantech.com.tw>
Signed-off-by: wei.zeng <wei.zeng@advantech.com.cn>
Signed-off-by: Ying-Chun Liu (PaulLiu) <paul.liu@linaro.org>
Cc: uboot-imx <uboot-imx@nxp.com>
Cc: Peng Fan (OSS) <peng.fan@oss.nxp.com>
diff --git a/board/advantech/imx8mp_rsb3720a1/Makefile b/board/advantech/imx8mp_rsb3720a1/Makefile
new file mode 100644
index 0000000..eb6b18b
--- /dev/null
+++ b/board/advantech/imx8mp_rsb3720a1/Makefile
@@ -0,0 +1,24 @@
+#
+# Copyright 2019 NXP
+# Copyright 2022 Linaro
+#
+# SPDX-License-Identifier:      GPL-2.0+
+#
+
+ifdef CONFIG_TARGET_IMX8MP_RSB3720A1_6G
+obj-y += imx8mp_rsb3720a1.o
+
+ifdef CONFIG_SPL_BUILD
+obj-y += spl.o
+obj-$(CONFIG_IMX8M_LPDDR4) += lpddr4_timing_rsb3720a1_6G.o
+endif
+endif
+
+ifdef CONFIG_TARGET_IMX8MP_RSB3720A1_4G
+obj-y += imx8mp_rsb3720a1.o
+
+ifdef CONFIG_SPL_BUILD
+obj-y += spl.o
+obj-$(CONFIG_IMX8M_LPDDR4) += lpddr4_timing_rsb3720a1_4G.o
+endif
+endif